Heat exchanger



Sept. 1941- v R. NELSO N 2,254,383

w I HEAT EXCHANGER Original Filed Apg. 10, 1936 4 Sheets-Sheet l v 1/55 701 I R/cHA/w H Nam/v Sept. 2, 1941. R. H. NELSON 2,254,333

HEAT EXCHANGER Original Filed Aug. 10, 1956 4 Sheets-Sheet 2 Sept. 2, 1941. l

R. H. NELSON HEAT EXGHANGER Original Filed Aug. 10, 1936 4 Sheets-Sheet :5

m RICHARD H Nam/v Sept. 2, 1941.

H. NELSON HEAT EXCHANGER 4 Sheets-Sheet 4 Original Filed Aug. 10, 1936 RICHARD H NELSON parts in elevation,

Patented. Sept. 2, 19 1 HEAT EXCHAN GER Richard H. Nelson, 'Moline, IlL, assignor to The Herman Nelson Corporation, Moline, 11]., a corporation of Illinois Original application August 10, 1936, serial No. 95,141. Divided and this application May 25, 1939, Serial No. 275,587 I 7 Claims. (01. 126-118) The present invention relates in general to heat exchangers especially adapted for use in.

apparatus for the conditioning of air for circulation to rooms and the like, and while the heat exchanger may'be utilized in either cooling or heating apparatus, it will be described connection with a furnace.

g The present application constitutes a division of my United States Letters Patent No. 2,172,667.

The illustrated furnace with which the present invention is utilized embodies a compact unit, preferably employing oil as the combustion fuel and provided with an induction blower to create a stack draft and reduce the tendency of the gases of combustion to seep :into the air flow passages surrounding the combustion chamber and fiuesor ducts. Broadly, my heat exchanger as embodied in the furnace preferably utilizes flues or' ducts for thecombustiongases which are provided with fins or ribsboth inside and outside for the better transfer of heat from the combustion gases to the air flowing past the fiues or ducts, and with the ribs or fins spaced more closely where the temperature difference ent invention to provide a heat exchanger which is efficient in operation and economical to-conherein in struct; and which is provided with a'piurality of.

tubes so arranged that, when itis mounted in an air conditioning chamber, it will condition described.

On the-drawings:

Fi ure 1 is a longitudinal sectional view with of a furnace embodying my invention.

Figure 2 is a sectional view taken substantially along the line II--II of Fig. 1.

Figure 3 is a sectional view taken substantially along the line III-III of Fig.1.

Figure 4 is a sectional view taken substantially along the line IV-IV of Fig. 1.

Y has a conduit 31 leading upwardly to a plurality Figure 6 is an enlarged detail view of the damper and control arrangement.

As shown on the drawings:

The reference-numeral [0 indicates generally an outer casing or housingformed of a suitable gauge of sheet metal and enclosing the various operative elements of a furnace embodying the features of my invention. Said housing l0 comprises end .walls It and 2, side walls I3 and M, a bottom wall I5 and a top wall l6 from which latter wall extends a stack I! for conducting the heated air to the branch ducts and thence to the registers used in heating the room, building,

or the-like. V I

The interior of said housing. I!) is divided by a horizontal plate I8 into a lower air intake and mixing space IS. The lower portion of the side.

blower or fan units 22 are mounted within said chamber I9 supported from the horizontal plate l8. Each. of said blower units includes a blower proper 23 mounted upon a horizontal axis 24,

the ends of which extend through bearing plates elongated cylindrical fire box having an outer shell 32 of metal and an inner refractory lining 33. At one end of said combustion chamber 3| oil burner equipment is mounted upon the plate l8, including a'draft casing 34,- which extends through an opening in said end of the combustion chamber. An oil supply pipe 35 leads to the oil burner, indicated generally by the reference numeral 36.

The other end of the combustion chamber 3| of longitudinally extending ducts 38 arranged in two sets or banks of three ducts each. Saidducts are flattened to present their narrow rounded lower portions 40 to the upwardly ascending air currents and their flattened faces H are ar ranged in closely spaced parallel relation to provide passages 42 therebetween. At the further J end from the intake duct 31, a header box 43' (Fig. 5) extends across all of the horizontal ducts 38 to direct the flue gases issuing from the first set, of ducts into the second set of ducts. From the second set of ducts, the flue gases pass through a' header box 44 into the housing of an induction blower 45 and thence are delivered to a stack (not shown).

Each of the ducts 38 is provided internally with longitudinally extending fins or ribs 46, which may suitably take the form of channel strips riveted or otherwise secured to the inner flat vertical surfaces of the ducts. These fins or ribs 46 serve to absorb and transfer the heat from the flue gases to the me a1 walls of the ducts I for radiation into the air passing around and outside of the ducts. Fins or ribs 41 are also secured to the outside fiat walls of said ducts 38, said fins or ribs taking the form of angle irons 48 or channel irons 49, depending upon their position along the length of said ducts.

I have found that more eflicient heat transfer can be effected if the outer fins or ribs 41 have.

substantially a logarithmic spacing,-the ribs or d is largely equalized throughout the length of said ducts by virtue of the greater radiating surface area where the temperature of the flue gases passing through the ducts is lower. a

The driving mechanism (Figs. 1 and 3) comprises a motor 50, suitably mounted withinthe lower compartment 19 at one end thereof, and having a shaft 5| to which are keyed a pair of pulleys 52. One of said pulleys 52 drives a pulley 53 on the shaft 24 through a belt 54. A second belt 55 is trained around a pulley 56 secured on a pump shaft 51 and around a pulley 58 secured on the induction blower shaft 55. Said second belt 55 is driven by the other of the pulleys comprising a pair of plate dampers 60 and 6| (Fig. 4) hinged at their lower edges, as at 52 the temperature of the furnace has dropped below a predetermined point. Such means comprise a horizontally extending frame portion 86 (Fig. 4) having depending from each end thereof a bimetal rod 61 carrying at its free end a cam shaped plate 68. Said plates 68 are provided with a lower arcuate shaped surface- 69 terminating at one end in a hooked portion 10.

The bimetal rods 61 are so constructed that upon being heated they bend in a plane parallel to the side walls l3 and I4, as best illustrated in dotted lines Fig. 6. The upper edges of the dampers 60 and BI are provided with stepped recesses II and 12 of less and greater depth, respectively. Normally, with the furnace cold as at the starting up of the furnace, the bimetal rods 61 are in vertical position and out of alignment with the recesses I2 and II, so that the (I cam plates 68 resist the opening of the dampers 60' and GI. The dampers therefore remain shut even after the motor has been started up and the blowers 23 set in operation. However, as the furnace heats up, due to the combustion of fuel within the combustion chamber 3|, the bimetal rods 61 bend until they assume the position indicated by the letter A, (Fig. 6). In

this position, the cam plates 68 are in alignment cooled down substantially, the bimetal rods 61 are in their extreme bent position indicated by the letter B (Fig. 6). In this position, the ends of the cam plates 58 overlie the edges of the recessed portions II of said dampers and GI to prevent the dampers from falling shut. As the furnace continues to cool down, the bimetal rods 61 come to assume the position indicated .by the letter A (Fig. 6), where the cam plates Bl are in alignment with the deeper recesses 12 and the dampers 60 and Cl are free to fall closed by reason of the counterweights I4 and 65. During and 63, respectively, ,from adjacent the side walls l3 and I 4. Said dampers 60 and 5|. extend substantially the full length of the combustion chamber 3| and in their closed position rest with their upper edges against the outer wall of said combustion chamber. In their open position. shown in dotted lines in Fig. 4. said dampers 60 and GI are substantially'vertical and par-- allel to the side walls 13 and I4. The dampers 'are of relatively light sheet metal construction and are provided, with angle irons 64 and'65 which serve as counterweights to cause the dampers to fall into closedposition whenthere is no air flow from the blowers 23. The flow of this interval while the furnaceis cooling of! and the dampers-are open. a natural convection of air through the furnace and the air ducts is permitted, so that the remaining sensible heat of 211116 furnace parts is utilized in the heating of e air.

In order to provide for humidiflcation and conditioning of the air heated by the furnace, an

air, when the blowers 23 are operating, is sufflcient to open the dampers 60 andil in the absence of any means for regulating their position.

Means'are provided, however, for regulating and controlling the dampers ill and GI so that these dampers will remain closed until after the furnace has been brought up to a predetermined evaporating pan 15 (Fig. 1) may be mounted above the. header 43. Said evaporating pan I5 is provided with a supply of hot water through a pipe 16 (Fig. 2) that is a part of the domestic hot water circulating system. The flow of hot water from the pipe 16 into'the evaporating pan 15 is controlled by means ofa thermostatic hu- 'midity control valve "which has a part 18 extending into the outlet ducts ll'from the furnace. A humidifier feed line 19 leads from said valve Tl to control the flow of hot water from said pipe 18 into the evaporating pan II. An overflow line conducts the excess of water from said evaporating pan 15 to waste.

The electrical circuit for energizing the motor 50 includes a control box 4| (Fig. 2) from which a conduit. 82 leads tothe motor 50 and to a transformer primary within a housing l3.

'to the other of the duct.

I am aware that many changes may be made and numerous details of construction may be varied through a wide range without departing from the principles of this invention, and I, therefore, do not purpose limiting the patent granted hereon otherwise than necessitated by the scope of the appended claims.

I claim as my invention:

1. In a furnace, a plurality of waste flue ducts disposed in a horizontal plane and each having longitudinally extending heat absorbing ribs on the inside and vertically extending heat radiating fins on the outside thereof, said outside fins being spaced more closely together along the lengths of said ducts the lower the temperature gradient between the inside and outside of said ducts. V

2. In heat exchange apparatus, an 'air conditioning chamber having an inlet and outlet opening, and a plurality of horizontally disposed,

ducts extending across said chamber for conducting a fluid for changing the temperature of air passingthrough said chamber, fluid flow insaid ducts being in the same direction, and each of said ducts having heat exchange surfaces of increasing area per unit length of duct in the direction of the flow of said fluid.

3. In a device of the character described, a casing having an inlet and outlet for a fluid medium to be passed therethrough and be heated, a duct for the passage of a heating medium, said duct forming a single pass for the heating medium across the interior of the casing between ing a combustion chamber and a separate surrounding casing in spaced relation thereto, said casing having an inlet for the admission of air and an outlet for the delivery and .distributizn of heated air, tubes for conducting the hot gases away from said combustion chamber, said tubes traversing the space within the casing in a horizontal plane between said inlet and outlet and sage of a fluid conditioning medium, said second duct consisting of a plurality of tubes traversing said first duct in a plane extending thereacross between its ends and defining a plurality of series connected passes in the first duct for the conditioning medium, and fins carried by said tubes, the flns on each tube of the passes bein progressively spaced along the tube at intervals its inlet and outlet and having laterally prdjecting external fins progressively spaced along said duct at intervals decreasing from one side of the casing to the other in the direction of the flow of the heating medium in the ducts, whereby the medium in the casing engaging said duct and fins will be uniformly heated from one end 4. In a device of the character described, a casing having an inlet and outlet for a fluid medium to be passed therethrough and heated, a plurality of subtsantial Parallel ducts defining a single pass through the casing for the passage of a heating medium in the same direction of flow, said ducts longitudinally extending through the interior of the casing and horizontally disposed between the inlet and outlet thereof, and

external fins progressively spaced along said ducts at intervals decreasing in [the direction of the fluid flow therethrough, whereby the medium passing through the casing will be uniformly heated along said ducts.

decreasing in the direction of flow of the conditioning medium therethrough, whereby thefluid at the respective passes of the conditionin medium will be uniformly conditioned as to its temperature along said tubes.

7. In heat exchange, apparatus, a first duct for the passage of avfiuid to be conditioned as to its temperature, said duct having a fluid inlet and a fluid outlet, a second duct for the passage of a fluid conditioning medium, said second duct consisting of a plurality of tubes traversing the first duct in a plane extending thereacross between its ends and defining a plurality of series connected passes in the first duct, the tubes of each of said passes constituting parallel flow paths for said medium, and fins carried by said tubes, the fins of each tube of the passes being progressively'spaced along the tube at intervals decreasing in the direction of flow of the conditioning medium therethrough, whereby the fluid at the respective passes of the conditioning medium will be uniformly conditioned as to its temperature along said tubes.

RICHARD H. NELSON.

5. In a furnace of the character described hav-' 

